In a conventional semiconductor device, an Er silicide is used as a gate electrode of an n-MOSFET (Metal Oxide semiconductor Field Effect Transistor) and a Pt silicide is used as a gate electrode of a p-MOSFET.
The Er silicide has an effective work function, which is lower than the middle of the band gap of Si, and the Pt silicide has an effective work function, which is higher than the middle of the band gap of Si.
However, the various metals (Er and Pt) are used in the gate electrodes in single semiconductor device. So, the manufacturing process may be complicated and through put may be worsened.